FIELD OF THE INVENTION
[0001] This application is a continuation-in-part of application Serial No. 06/946,146 filed
December 22, 1986 which is a continuation-in-part of application Serial No. 06/620,647
filed June 14, 1984, now abandoned, which is a continuation-in-part of application
Serial No. 562,779 filed December 19, 1983, now abandoned.
[0002] The present invention relates generally to a method for coating substrates with a
uniform adherent coating. More particularly, the invention discloses a process for
condensing vaporized, unsaturated monomers on a rapidly-moving substrate and curing
the deposited monomer,
in situ, by employing a radiation source such as electron beam, U.V. radiation, or the like.
The resultant cured films are extremely thin--generally less than 4 microns thick--
but function as protective coatings for the underlying substrate or as a base for
a subsequent coating.
[0003] This invention is related to the following co-pending, commonly assigned, patent
applications: Serial No. 562,873, filed December 19, 1983, entitled "Capacitor With
Resin Dielectric And Method Of Making"; Serial No. 562,871, filed December 19, 1983,
entitled "Capacitors Containing Polyfunctional Acrylate Polymers As Dielectrics";
Serial No. 562,893, filed December 19, 1983, entitled "1; 2-Alkanediol Diacrylate
Monomers And Polymers Thereof Useful As Capacitor Dielectrics"; Serial No. 562,872,
filed December 19, 1983, entitled "Acrylate-Containing Mixed Ester Monomers And Polymers
Thereof Useful As Capacitors Dielectrics"; and Serial No. 562,894, filed December
19, 1983, entitled "Polyfunctional Acrylate Monomers For Polymers Thereof Useful As
Capacitor Dielectrics", all of which are hereby incorporated by reference. This application
is also related to Serial No. , filed simultaneously herewith.
BACKGROUND OF THE INVENTION
[0004] There are increasing numbers of applications for articles coated with thin films
of organic coatings. For example, an economically produced thin film coating having
particular properties can be used in food packaging or as a protective coating for
metal or other substrates used in information display, medicine, instrumentation.
While coating systems are available in the art, unfortunately, systems presently available
operate at speeds which are too slow to be economically justified or the coating produced
is not satisfactory for the particular substrate to be coated or the environment in
which the substrate exists.
[0005] Illustrative of such systems is a coating process disclosed in British Patent Specification
1,168,641 published October 29, 1969. That process involves coating substrates by
vaporizing a reactive material which is deposited (under vacuum) on the surface of
a substrate. The coated substrate is then exposed to electron beam, X-rays, or gamma
rays in order to cross-link or cure the deposited material. The British reference
discloses a number of polymers and monomers which can be employed as reactive materials,
including monomeric acrylates having a single, reactive double bond. The rate of
deposition of curable materials, however, is not satisfactory for many applications;
the deposition rate being disclosed as one micron/second with the curing being accomplished
in times varying from one second to one minute.
[0006] It is an object of the present invention to provide a thin film coating which can
be produced relatively economically and at a relatively high speed of production.
[0007] It is further an object of the present invention to provide a coating structure that
has mechanical and electrical properties which are useful in a variety of coating
applications.
SUMMARY OF THE INVENTION
[0008] The invention disclosed and claimed herein serves to achieve the desired objectives
and to obviate problems associated with the prior art. The present invention provides
for a method of coating a substrate with a cured coating at an extremely rapid rate.
The coating is quite thin, and has the designed properties sought for many applications
in that it is substantially continuous (i.e., pinhole and void free) as well as substantially
delamination free. In contrast to procedures heretofore utilized in the art, such
as recited in British Patent Specification 1,168,641, which disclose maximum coating
speeds in the range of 1 x 10⁻³ cm/sec, the process of the present invention operates
optimally at a rate of 100 cm/sec - five orders of magnitude faster.
[0009] The method of the present invention provides a process for coating a substrate with
a continuous polymer film. The resultant films formed by the method of the present
invention have a thickness of less than four microns, and preferably less than two
microns. Continuous uniform films at least as thin as 0.1 microns can be fabricated.
The films are formed by depositing a vapor of curable monomer, under vacuum, on a
movable substrate which is mounted in thermal contact with a rotating drum which is
maintained at a temperature below the boiling point of the vaporized monomer. As a
result of this temperature differential, the monomer vapor condenses on the surface
of the substrate.
[0010] The monomeric materials utilized in the present invention are relatively low in molecular
weight, between 150 and 1000, and preferably in the range 200 to 300. Polyfunctional
acrylates or mixtures of monofunctional acrylates and polyfunctional acrylates are
especially preferred. The monomers or monomer mixtures employed have an average of
about two or more double bonds (i.e., a plurality of olefinic groups) and have vapor
pressures between about 1 x 10⁻⁶ Torr and 1 x 10⁻¹ Torr, most preferably a vapor pressure
of approximately 10⁻²Torr at standard temperature and pressure, (i.e., relatively
low boiling materials). These high-vapor pressure monomers can be flash vaporized
at relatively low temperatures and thus are not degraded (cracked) by the heating
process. The absence of unreactive degradation products means that films formed from
these low molecular weight, high-vapor-pressure monomers have reduced levels of volatile
components. As a result, substantially all of the deposited monomer is reactive and
will cure to form an integral film when exposed to a source of radiation. These properties
make it possible to provide a substantially continuous coating despite the fact that
the deposited film is very thin. The cured films exhibit excellent adhesion and are
resistant to chemical attack by organic solvents and inorganic salts.
[0011] Specifically, in one embodiment, the process of the invention is carried out in an
vacuum chamber containing a movable support such as a rotating drum, the surface of
which is maintained at a temperature sufficient to permit condensation of a material
deposited thereon. Although the temperature will vary depending on the monomer (or
monomer mixture) utilized, generally a temperature in the range of about 40°-70°C
will be appropriate.
[0012] A vapor outlet of a flash vaporizer is mounted adjacent to an upstream portion of
the support and a curing means is mounted adjacent to a downstream portion of the
support. The chamber is evacuated until the pressure is less than about 1 X 10⁻¹ Torr
and preferably 1 X 10⁻⁵ Torr. A curable monomer component with the properties mentioned
above is metered to a heated flash vaporizer system where the material is atomized,
vaporized and condensed on the surface of the movable support which travels at a speed
of between 1 and 1000 cm/second. The condensed film is less than 4 microns thick.
[0013] Curing is accomplished by opening the double bonds of the reactant molecules. This
can be accomplished by means of an energy source such as apparatus which emits infra
red, electron beam, thermionic or ultra violet radiation.
[0014] The process of the present invention is particularly suitable for coating flexible
substrates such as paper, fabrics, thin metal, plastics such as polyesters, polyethers,
polyolefins, and the like, or virtually any flexible material. After curing, the film-covered
substrate can be coated with additional materials, such as metals (e.g., aluminum)
or other polymers. The products of the coating operation can be used, for example,
in optical filters, coatings for window treatments, or coatings for packaging.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Other aspects of the present invention will become apparent to one of ordinary skill
upon consideration of the following detailed description and reference to the attached
drawings, in which:
FIG. 1 shows a schematic view of one embodiment of apparatus and system for carrying
out the process of the invention;
FIG. 2 shows a schematic view of a second, preferred embodiment of apparatus and system
for carrying out the process of the invention;
FIG. 3 shows a fragmentary schematic view of an embodiment of a monomer feeding system
for depositing a metered amount of monomer to be deposited on a movable support;
FIG. 4a shows a fragmentary perspective view of another embodiment of a movable support
with the support being a rotatable disk;
FIG. 4b shows a fragmentary perspective view of further embodiment of a movable support
with the support being a continuously or intermittently indexed rotatable disk;
FIG. 4c shows a fragmentary perspective view of yet another embodiment of a movable
support with the support being a reciprocating plate with the reactive monomer being
deposited on a substrate located on the bottom wall of the plate;
FIG. 4d shows a fragmentary perspective view of still another embodiment of a movable
support in which a moving web substrate serves as the support and a reactive monomer
is deposited on the bottom wall thereof;
FIG. 5 shows an enlarged, partially sectioned, diagram of a portion of the apparatus
shown in FIG. 1;
FIG. 6 is an alternate apparatus to that shown in FIG. 5;
FIG. 6a shows an enlarged partially sectioned, diagram of a preferred dielectric flash
evaporator apparatus;
FIG. 7 is a fragmentary perspective view, partially sectioned, of a portion of the
apparatus shown in FIG. 1; and,
FIG. 8 is a sectional view taken along the line 8-8 in FIG. 7.
DETAILED DESCRIPTION
[0016] While the invention will be described in connection with preferred embodiments and
procedures, it will be understood that we do not intend to limit the invention to
those embodiments or procedures. On the contrary, we intend to cover all alternatives,
modifications and equivalents as may be included within the spirit and scope of the
invention as defined by the appended claims.
[0017] One form or embodiment for practicing the method of the present invention is illustrated
in FIG. 1 which illustrates apparatus arranged within and around a chamber 30 which
is either an vacuum chamber capable of maintaining a vacuum, or a housing divided
into vacuum portions. Within a vacuum environment is a movable support in the form
of a movable support 31, a dielectric or monomer deposit system 32, a monomer curing
system 33, and an optional metal material deposit system 34. A substantial vacuum
is required, down to the order of 1 X 10⁻⁵ Torr.
[0018] Movable support 31 is a water cooled drum 35 driven by a motor 36 whose outer cylindrical
surface 37 defines a rapidly moving continuous surface passing through a dielectric
or polymer layer forming zone and an optional metal forming zone. The regions in which
the drum surface 37 and the systems 32, 33 are located constitute the dielectric or
polymer layer forming zone, and the region in which the drum surface 37 and the system
34 are located constitute a metal forming zone. Drum rotation creates the machine
direction 26, which is the direction the surface or support passes through the upstream
dielectric forming zone and the downstream metal forming zone.
[0019] Because of the small dimensions involved, the surface 37 should be smooth and true.
A sheet or substrate 13 of a flexible material is firmly secured to the drum 35 and,
when in place, the outer surface of the substrate defines the surface 37. The drum
35 is cooled to a temperature specific to the particular monomer being used and generally
in the range of 20°C to 80°C to facilitate condensation of the vapor deposits, and
the apparatus functions at drum surface speeds of 1 to 1000 cm/second.
[0020] The optional metal/inorganic material deposit system 34 includes a conventional electron
beam vaporization device 41 or a group of resistive evaporation sources (boats) such
as those used for metallizing film within a vacuum environment or a sputtering target.
The rate of vaporization can be sensed by a quartz monitoring device 42 providing
feedback for controlling the rate at which aluminum is vaporized by the device 41.
The pattern in which aluminum vapor is deposited can be controlled by a mask, in this
case a shadow mask 43, having openings through which the vapor passes.
[0021] Referring now to FIGS. 1 and 5, as a feature of the invention, the dielectric deposit
system 32 flash vaporizes a dielectric in monomer form, and the smaller gaseous molecules
are guided under moderate differential pressure through nozzles 64 onto the surface
37 of substrate 13.
[0022] The monomeric materials employed in the process should provide an average of about
two or more olefinic groups per molecule. By way of example, a single diolefinic material,
mixtures of two diolefins, or mixtures containing a polyolefin and a monolefin can
be employed. If multiple components are utilized, the components can be metered into
an evaporator individually or as a single mixture.
[0023] Due to their low molecular weight and the presence of an average of about two or
more olefinic groups, the monomers (or monomer mixtures) utilized are highly reactive.
As a result, the monomers can be deposited and cured at rapid speeds, viz, 1 to 1000
cm/sec.
[0024] Because of their reactivity, physical properties, and the properties of cured films
formed from such components, polyfunctional acrylates are particularly useful monomeric
materials. The general formula for such polyfunctional acrylates is:

wherein:
R¹ is an aliphatic, alicyclic or mixed aliphatic-alicyclic radical derived from a
compound of the formula R¹(OH)
m;
R² is hydrogen, methyl, ethyl, propyl, butyl or pentyl;
n is from 2 to 4;
m is 2 or more.
[0025] Such polyfunctional acrylates may also be used in combination with various monoacrylates,
such as those having the formula:

wherein:
R², r and 2 are defined above;
x¹ is H or:

X³ is CN or COOR³ wherein R³ is an alkyl radical containing 1-4 carbon atoms. Most
often, X³ is CN or COOCH₃.
[0026] Diacrylates of the formula below are particularly preferred:

wherein:
r and s are each 7 or 8 and the sum of r and s is 15.
[0027] The diacrylates:

and alkoxylated cyclohexane dimethanol diacrylates (wherein the alkoxy group contains
1 to 4 carbon atoms) are especially suitable.
[0028] The monomer in liquid form is fed through a line 57 and control valve 56 to the open
end of the horn 58 of an ultrasonic atomizer 59. The resulting micro droplets impinge
on the inner walls of a vaporization tube 61 heated by band heaters 62 to an appropriate
temperature, approximately 100- 400°C. for the acrylate resins referred to above.
The liquid is thus instantaneously vaporized, i.e., flash vaporized, so as to minimize
the opportunity for polymerization prior to being deposited on the substrate.
[0029] Pressure in the tube 61, at about 1 Torr, causes a monomer gas stream to flow through
nozzles 55 for deposition and condensation. The nozzles 55 are heated by conduction
from the tube 61 to minimize condensation before the gas stream leaves the nozzles.
[0030] The thickness of the monomeric coating is dependent upon the time of deposit, i.e.,
the length of the nozzles 55 relative to the speed of the surface 37, and the rate
of monomer flow through the valve 57.
[0031] An alternate arrangement for atomizing the liquid monomer is suggested in FIG. 6
wherein the monomer is directed through a capillary tube 68 to a point closely adjacent
the horn 58 of the ultrasonic atomizer 59. In this arrangement, a meniscus is formed
between the end of the capillary tube 68 and the end of the horn 58, and the monomer
is drawn uniformly through the tube.
[0032] Another system which is preferred for atomizing the liquid monomer is shown in FIG.
62 in which monomer is directed through capillary tube 200 to a point closely adjacent
ultrasonic atomizer 201. The monomer droplets are atomized ultrasonically and the
droplets vaporized by the means of heating elements 203, 204 which heat the walls
of atomization chamber 205. The vaporized monomer passes through a top hat shaped
baffle 206, screen 207 and nozzle 208, where it condenses on the movable support,
now shown. Nozzle 208 is shaped to conform substantially to the shape of the surface
of the movable drum.
[0033] Other systems which may be utilized for depositing a monomeric film on a substrate
are disclosed in pending Application Serial No. 877,175 filed June 23, 1986 of Angelo
Yializis entitled, "Flash Evaporation of Monomer Fluids", pending patent Application
Serial No. 900,941 filed August 25, 1986 of Gregg Bischoff entitled, "Monomers Atomizer
For Evaporation" and in Application Serial No. 850,427 filed April 8, 1986 of Mooyoung
Ham entitled, "Atomizing Device For Vaporization", the disclosures of which are incorporated
by reference herein.
[0034] Referring now to FIGS. 1, 7 and 8, the condensed liquid monomer is radiation cured
by the second system 33 in the dielectric forming zone which includes a radiation
source, preferably a gas discharge electron beam gun 70. The gun 70 directs a flow
of electrons from a housing chamber 71 through an emitter window 72 onto the monomer,
thereby curing the material to a polymerized cross linked form capable of withstanding
high temperatures. Curing is controlled by matching the electron beam voltage to the
dielectric thickness. For example, a 10 Kv electron voltage will penetrate about
1 micron of deposited monomer.
[0035] The gun 70 includes a rectangular copper cathode 73 supported by a connector 74 in
an insulator 75 mounted in a ground shield 76 that is fixed to the housing 71. A tungsten
mesh extraction screen 77 is fixed across the window 72. A gas such as argon is fed
to the housing chamber 71 through a line 78 and a control valve 79. An electrical
potential is imposed between the cathode 73 and its connector 74, and the shield 76,
housing 71 and screen 77, with the result, keeping in mind the vacuum environment,
that a gaseous plasma is created in the housing, primarily between the cathode 73
and the screen 77. The cathode is preferably formed with grooves 81 on its face so
that electrons are expelled in a non-linear beam to substantially fill the housing
chamber 71. Because of the plasma created, other electrons are stripped from the ionized
gas molecules in different portions of the chamber, a so-called field enhanced effect,
with the result that electrons at widely varying energy levels are emitted from the
window 72. The wide range of energy levels of the emitted electrons is believed to
cause the observed effect that the monomer is cured with little surface charging.
Other types of electronic guns (i.e., thermionic guns) can be employed.
[0036] FIG. 2 illustrates a second, preferred embodiment of apparatus which can be employed
in the method of the present invention. There is shown within a vacuum environment
in a vacuum chamber 101a or a housing divided into vacuum portions, a movable support
in the form of a rotatable drum 100 having a cooled surface 101 driven by a motor,
not shown. A liquid monomer delivery, metering and deposit system 102, a monomer curing
system 104, and a metal or inorganic material deposit system 106 are also shown.
The movable drum support 100, the vapor outlet of the monomer flash vaporizer, the
curing means and optional inorganic material deposit apparatus 106 are disposed within
the vacuum environment.
[0037] Drum 100 continuously rotates the cooled drum surface 101 through an upstream polymer
layer forming zone. The region in which surface 101 passes the monomer condensation
and downstream curing systems 102, 104 constitutes the polymer layer forming zone,
whereas the region in which the drum surface 101 passes the inorganic material deposit
system 106 constitutes the inorganic or metal forming zone.
[0038] Deposit system 106 is optional. If desired, inorganic material deposit system 106
could be eliminated if a single layer of organic coating is all that is desired. Alternatively,
system 106 could be replaced by a second liquid monomer delivery, metering and deposit
system (not shown) similar to system 102. This second monomer system could be used
to deposit a second layer of the same or different monomer mixture on the substrate,
if desired.
[0039] Referring to FIGS. 2 and 3, a liquid monomer at room temperature is deposited in
reservoir 112 where it passes to a deareator 113 where the monomer is stirred and
degased at a temperature of about 25°C by pulling a vacuum to remove gases entrained
in the monomer to preclude, insofar as possible, any pressure variation in the monomer
evaporator. The monomer then passes through valve 114 to a conventional piston pump
116 which pumps the monomer under suitable pressure and temperature to a monomer metering
means 118 which meters a desired amount of monomer to ultrasonic atomizer 120 through
constricted conduit 121 which provides a positive back pressure for the monomer entering
atomizer 120. The monomer is atomized and forms micro droplets which are heated to
an appropriate temperature, approximately 100-400°C. for the acrylate resins referred
to above. The droplets are instantaneously vaporized, i.e., flash vaporized, in evaporator
122 to minimize the opportunity for polymerization and the vaporized monomer condenses
on the cooled drum surface 101. A flow rate of the monomer through the constriction
121, generally in the range 0.5 to 10 cc/min. has been found satisfactory with the
flow rate being dependent upon the speed of the movable support, the desired layer
thickness, and the width of the deposit. The monomer is metered in order that the
amount of monomer entering atomizer 120 will be the optimum amount deposited on the
movable support. It is important that the metered monomer material is deposited on
the movable support, otherwise the monomer will polymerize on the walls of the evaporator.
[0040] The condensed monomer liquid is subsequently radiation cured in the polymer or dielectric
forming zone which includes a radiation source, preferably a gas discharge electron
beam gun 124. Activation of gun 124 in the manner previously described for the electron
beam gun system of FIG. 1, causes a flow of electrons to be directed onto the monomer,
thereby curing the material to a polymerized cross linked form. In the embodiment
of FIG. 2, the gun is positioned to be aligned tangentially to the drum surface 101
in order that the flow of electrons contact the monomer tangentially as opposed to
the 90° angle disclosed in FIG. 1. It has been found that by positioning the gun in
the manner described for the embodiment of FIG. 2, the surface charge is reduced,
charging defects are eliminated, and a more uniform cure from the top to the bottom
of the monomer layer is achieved.
[0041] The cured monomer then passes to the optional inorganic material deposit system
106 where an inorganic material such as aluminum can, if desired, be deposited on
the cured monomer layer. An inorganic metal deposition system 126 is provided which
is similar to the mask retraction and shifting system shown in FIG. 1, which comprises
a controller 50, mask shifting motor 47, mask retractor motor 51 and removable shutter
52.
[0042] A controller 128 is connected to the drum motor, not shown, for sensing drum revolution.
Controller 128 serves to provide the appropriate signals to the monomer delivery system,
flash vaporization retractor 130, which positions the vaporizer the desired distance
relative to the drum surface, and the electron beam curing system for activating
the curing system. The controller 128 can also supply the appropriate shifting to
the mask retraction and shifting means, if a mask is employed.
[0043] If desired, the rotatable drum shown in FIGS. 1 and 2 can be replaced with other
types of movable supports. For example, referring to FIG. 4a, there is shown a rotatable
disk 160 which could serve as a movable support with a cured adherent film 162 being
formed on the surface of the disk. Again, turning to FIG. 4b, there is shown a disk
164 which is adapted to be rotated continuously or indexed intermittently at a desired
speed, past deposition and curing stations heretofore described, to provide a number
of coated substrates 166, 168.
[0044] FIG. 4c shows a movable support which comprises a reciprocating plate 170 having
a substrate 172 attached to a cooled surface 173. A cured monomer film 174 has been
deposited on substrate 173.
[0045] FIG. 4d shows a rotatable drum 176 with a water cooled surface 177. A moving web
substrate passes over rollers 178, 179, the rollers serving to maintain the moving
substrate in contact with the drum surface so that it can be cooled by the drum. While
the substrate is in contact with the drum surface, a monomer coating 180 can be applied
to the moving substrate and cured.
[0046] It is appreciated that other structures for movable supports, aside from those shown
and described herein, could be utilized by a person of ordinary skill in the art.
1. A high-speed process for coating the surface of a substrate with an adherent film
comprising the following steps:
(a) providing a vacuum chamber containing: i) a movable support, ii) a vapor outlet
of a vaporizer mounted adjacent to an upstream portion of said support, iii) curing
means mounted adjacent to a downstream portion of said support, and, iv) means for
maintaining said support at a temperature below that of said vaporizer;
(b) placing said substrate in thermal contact with said movable support in a manner
permitting the surface of said substrate to move sequentially past said vapor outlet
and said curing means;
(c) evacuating gas from said chamber until the pressure within said chamber is less
than about 1 X 10⁻² Torr;
(d) selecting a curable component having an average of about two or more olefinic
groups per molecule, an average molecular weight between 150 and 1000, and a vapor
pressure in the range of 1 X 10⁻⁶ to 1 X 10⁻¹ Torr at standard temperature and pressure;
(e) metering a quantity of said curable component into an inlet portion of said vaporizer;
(f) vaporizing said component within said vaporizer;
(g) moving said support at a speed sufficient to pass said substrate relative to said
vapor outlet and said curing means at a rate between about 1 cm/sec and 1000 cm/sec;
(h) condensing a film of said component on the surface of said substrate, said film
having a thickness of less than 4 microns; and
(i) activating said curing means whereby a adherent film is formed on said substrate
surface.
2. The process of claim 1 wherein said vaporizer comprises means for flash vaporization
of said curable component.
3. The process according to claim 1 wherein said curable component is selected from
the group consisting of polyacrylates and mixtures of monoacrylates and polyacrylates.
4. The method of claim 3 wherein said polyacrylate has the formula:

wherein:
R¹ is an aliphatic, alicyclic or mixed aliphatic-alicyclic radical derived from a
compound of the formula R¹(OH)
m;
R² is hydrogen, methyl, ethyl, propyl, butyl or pentyl;
n is from 2 to 4;
m is 2 or more.
5. The method of claim 3 wherein said monoacrylate has the formula:

wherein:
R², r and 2 are defined above;
x¹ is H or:

X³ is CN or COOR³ wherein R³ is an alkyl radical containing 1-4 carbon atoms.
6. The method according to claim 3 wherein said polyacrylate comprises a diacrylate
of the formula:

wherein:
r and s are each 7 or 8 and the sum of r and s is 15.
7. The method of claim 3 wherein said polyacrylate is selected from the group consisting
of:
(a) 1,6-hexane diol diacrylate;
(b) alkoxylated cyclohexane dimethanol diacrylates wherein the alkoxy group contains
1 to 4 carbon atoms; and

8. A process according to claim 1 wherein said movable support comprises a rotating
drum, rotatable disk or reciprocating plate.
9. The method according to claim 1 wherein said movable support is maintained at a
temperature in the range of about 20°C to about 80°C.
10. The method of claim 1 wherein said curing means comprises a gas discharge electron
beam aligned tangentially to said film on the surface of said substrate.
11. The method of claim 1 wherein said vaporizor is maintained at a temperature between
approximately 100 and 400°C.
12. The method of claim 1 wherein said curable component has a molecular weight in
the range 200 to 300.
13. The method of claim 1 wherein said substrate is flexible and is selected from
the group consisting of paper, fabrics, thin metals and plastics.
14. The method of claim 13 wherein said flexible substrate is a plastic selected from
the group consisting of polyester and polyolefins.
15. The method of claim 1 further including the step:
degassing said curable component prior to metering said component into said vaporizer
inlet.